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February 11, 2009 > TechKnow Talk: All that dazzles is not diamond

TechKnow Talk: All that dazzles is not diamond

It is one of life's unforgettable moments. A nervous young man presents his intended bride with a diamond ring and requests her hand in marriage. The sparkling, iridescent colors seem to leap out of the highly polished stone. The young woman, overcome with its beauty, quickly assents and falls into his arms, tears of joy streaming down her face.

The diamond has become a key component of this ritual. How was it created, what makes it so beautiful, and why is it so expensive? How did diamonds become so popular? Why are they associated with engagement and marriage? Finally, what is the future of the diamond business?

A diamond is unique in several ways. First, it is a mineral composed of only one element: carbon. Second, it is the hardest naturally occurring substance in the world, several times harder than the next-hardest mineral. The tightly packed crystal structure that accounts for this extreme hardness also renders diamonds easy to split in certain directions. Diamond cutters are careful to create a finished product with none of these vulnerable cleavage planes exposed.

By the way, a diamond will scratch imposter materials such as glass or cubic zirconium, but a gem should never be tested in this way, as diamonds will also scratch other diamonds, damaging both in the process.

The incredible "fire" of polished diamonds is due in part to their transparency to light from the entire visible spectrum. They transmit light from across the whole rainbow. In addition, they possess excellent dispersion, meaning they are very effective at separating, or refracting, the component colors of sunlight or other white-light sources, creating the prismatic effect.

Diamonds are formed deep within the earth. Carbonaceous (carbon-containing) material must be exposed to specific conditions, including high pressure (700,000-800,000 pounds per square inch) and high temperature (2000 degrees Fahrenheit) for a long time. These conditions are found only in certain locations about 100 miles below the surface of the Earth.

Occasionally, volcanic activity thrusts magma from these deep regions to locations much nearer the surface, carrying diamonds along for the ride. These may become diamond mines, sources of primary deposits. Secondary, or alluvial, diamond deposits are found on the surface, where they have been carried by the erosive action of water.

Alluvial surface deposits in India account for the use of diamonds as jewelry there for thousands of years. Diamond mining, leading to large-scale production and creating a world market, began about 130 years ago. Currently, about 140 million carats (approximately 7 tons) are mined annually, mostly in Russia and Africa, leading to about 30 million carats of cut and polished gems.

Most mined diamonds are not of sufficient size and quality to be used for gemstones and are instead destined for industrial uses. These include machining, grinding and cutting tools, abrasives, and various applications in the electronics industry. About 100 million carats of natural diamonds, and 30 times that amount of synthetic diamonds, are used annually for industrial purposes.

Due to low manufacturing costs of synthetic, laboratory-created diamonds relative to diamond mining, they have dominated the market for industrial diamonds since their invention in the 1950s. The original method used to create these diamonds is high-temperature, high-pressure, in which huge presses recreate the conditions that form natural diamonds.

A more recent technique showing great promise to create flawless synthetic diamonds is chemical vapor deposition. A "seed" or substrate, embedded with carbon atoms in the proper crystalline structure, is exposed to carbon plasma, which gradually deposits onto the seed material. This grows a diamond crystal in much the same way silicon crystals are grown here in the Bay Area for the semiconductor industry.

Because of diamonds' dense crystal structure, only a few elements are small enough to squeeze in between the carbon atoms as impurities. By controlling the type and amount of impurities, diamonds of various colors are produced. The most common impurity is nitrogen, which results in a pale yellow color, but other elements are used to produce orange, blue, or pink tints. These colored stones are rare and highly prized in nature, but easily produced synthetically.

These techniques have only recently become sufficiently sophisticated to produce diamonds of gem quality, indistinguishable from natural, mined diamonds. They are marketed as "cultured" diamonds. To date, most gem-quality synthetics are of relatively small size, less than one carat.

The diamond industry is unique, dominated by a few, large companies controlling the mining, cutting, distribution, and wholesale trade. The largest of these companies, De Beers, along with its subsidiaries such as the Diamond Trading Company, produce or market more than half of the world's diamonds.

De Beers enjoys one of the most successful advertising campaigns of all time. They hired the venerable advertising firm of N. W. Ayer & Son in the 1940s to popularize their product. The resulting campaign is still underway today, focused on associating diamonds with celebrities and other highly successful people, and of course with love and romance. "A diamond is forever," introduced in 1948, remains one of their most memorable slogans. The world market for diamonds has been growing ever since and is expected to reach about $60 billion this year.

This business climate, offering high demand and limited competition, allows for significant markup of diamonds as they travel through the supply chain. A diamond that cost less than $500 to mine may sell for $1,000 as a rough diamond, $1,500 after being cut and polished, $3,000 wholesale, and $6,000 in a retail outlet. By comparison, an identical cultured diamond may retail for $1,000. This is just an example; synthetic diamond prices vary tremendously, based partly on the method of manufacture.

It's not surprising that the diamond industry is concerned about the potential implications of cultured diamonds. Since it is made from very different material, cubic zirconium can easily be distinguished from natural diamond with any of several simple tests, such as hardness or thermal conductivity. But a synthetic diamond is essentially identical to its natural counterpart. De Beers has very recently marketed spectrometers which they claim can identify a synthetic diamond, but these are not in widespread use.

Synthetics pose risks not only to those companies in the diamond business, but to the consumer as well. Suppose an unethical retailer were to market synthetic diamonds as natural, pocketing a huge markup. Without some way to track the source of the diamond, who would know?

Perhaps a more interesting question is whether consumers would care. After all, they did get a "real" diamond. Would the customer care if it spent a billion years underground or a week in a laboratory? Would the recipient be more likely to reject her suitor bearing a cultured diamond?

There is one issue that consumers do seem to care about, that of "blood diamonds" or "conflict diamonds." These are diamonds produced by violent rebel groups who seize African mines and sell the diamonds to fund brutal revolutionary actions. Some industry experts estimate 2-3 percent of diamonds currently on the market may have such a history. In response to public outcry, the diamond industry has been struggling for methods to ensure that more of these diamonds do not find their way onto the market. Cultured diamonds present a guilt-free alternative for the consumer.

To address the market threats posed by synthetics, natural diamond producers are working with the synthetic manufacturers to institute a method of tracking diamonds to their source. So far, there seems to be cooperation among these groups, and cultured diamonds are currently engraved with microscopic serial numbers indicating their origin.

As more laboratories gain the technology to produce gem-quality stones, however, it will become increasingly difficult to control cultured diamond production. It is probably inevitable that synthetic diamonds will become mixed in with the supply of natural diamonds before long.

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